At last gives the differential relationships between the unknown parameters and the true errors of the observations. These relationships can be used to evaluate the precision of the estimations.

Based on the relation between true error and residual error, the author puts forward a characteristic method for detecting and locating multidimensional gross errors.

By its adjustment procedure, the effect formula of initial-bearing's error on adjustments of a straight and equal-side connecting traverse are introduced with the method of true error analysis.